[seekertom]

hi, y'all! noobie here, but born loong ago, and still have a yen to learn new things.

latest project is trying to get my 17hp briggs engine/tractor back on line. two problems with it. 1st is no spark. probably magneto coil is shot, but i don't want to just replace it. that's no fun, right?

i'm hoping to rig up a vintage car coil and points system, but not sure about the ballpark where the spark ought to occur, with respect to position of the flywheel magnet.

the magnetron has two poles, so i'm wondering if it sparks twice, once for each passing of the magnet across one of the poles, or just once.

next, i'm wondering on a good starting point to place a flywheel bump to open the points. ought to be fairly simple to make the mount adjustable, once it's in the ballpark.

to be more concise, at what point of the flywheel rotation does spark occur, with respect to the position of the flywheel magnet?

any idears where to begin?
thanks, st
ps 2nd problem i'll post separately so i don't confuse myself!:wave::wave:

 

[dirksenshoe]

The idea is to break the induced primary circuit of the magneto when its at maximum current. Depending on how the coil is built on your magneto will determine when the points should open and induce a max voltage in the secondary section of the magneto coil to give the hottest spark. Most of these system have two laminated iron bars that the flywheel magnet slides under. Current saturation in the primary occurs when the magnet on the flywheel is in the middle position exactly between the magneto's two bars. This would be the point you would like the points to break open to collapse the primary circuit for spark to occur. There some factors that could change this : mainly ignition advancement although you usually don't find this on older engines. I hope this helps. Long story short : when the magnet is exactly between the two ends of the coil.

 

[ratosupport]

Check the clearance between flywheel magnet and ignition coil

You may want to try checking the clearance between the flywheel and the coil first to make sure its not just spaced improperly.